Catalytic conversion of hydrocarbons



Patented Oct. l, 1940 y UNITED CATALYTIC CONVERSION oF HYDRO- f cARBoNscorporation of Maine Application July 9, 1936,` Serial No. 89,713

5 Claims.

This invention relates to a process for catalytically convertinghydrocarbons of relatively low boiling point and relatively poorantiknock properties into hydrocarbons having high antiknock ratings andsuitable for use as motor fuel in high compression engines. `Moreparticularly the process of the present invention relates to thecatalytic conversion of saturated hydrocarbons such as natural gasgasoline, straight run gasoline, propane, butane and similarhydrocarbons contained in natural gas into motor fuel gasoline of higheroctane number than the original stock.

Many processes have been devised for the reforming of straight rungasolines', naphthas and similar hydrocarbon mixtures in order toproduce gasolines of higher octane value. However, most of the processesemployed in such operations involve the use of extremely hightemperatures upwards of 1100 F. as well as high pressures. Someprocesses operate at slightly lower temperatures but excessively highpressures are vernployed. Temperatures of the order of 1300o F. andhigher are used for the conversion of hydrocarbons of the type of butaneand propane into constituents suitable as a gasoline motor fuel. Suchprocesses require expensive vand elaborate equipment and are in manycases economically impracticable because of the loss occasioned from theconversion of the hydrocarbons-into substany tially fixed gases such ashydrogen and methane. In the conversion of straight run gasoline andnatural gasoline to productsI of higher octane value, losses of thischaracter make the resulting products tooexpensive to warrant productionexcept for special purposes.

vThe `primary object of the present invention` therefore is to provide acatalytic process for converting hydrocarbons ofthe type referred tointo high octane products in a relatively simple and inexpensive manner.

A further object of'` the present invention is to provide a process forcatalytically converting relatively low boiling hydrocarbons into highoctane motor fuel products by the use of relatively low conversiontemperatures and moderate pressures.

Accordingly, the improved process of the present invention comprises thesteps of heating the hydrocarbon to be converted to a moderate tem#perature of from 750 to 850 F. and intimately contacting the heatedmaterial with a catalytic metallic salt comprising the iron, aluminum,copper, zinc, molybdenum, chromium, manganese or, nickel salts ofphosphoric acid, sulfuric acid,

hydrochloric acid, silicio acid or boric acid.

These catalytic materials may be for convenience deposited on inertcarriers such as fullers earth, coke particles, or other similarmaterial, or they may be used by themselves.

Other features and advantages of the process of the present inventionwill be apparent to those skilled in the art from'the following detaileddescription taken in connection with the accompanying drawing in which:

The single gure is a' diagrammatic ow sheet E@ illustrating anapparatusV particularly adapted for carrying out the improved process. f

Referring to the drawing the hydrocarbon to be converted which forvpurposes of illustration is natural gasoline, is introduced into thesystem B5 of the apparatus through a feed line 2 and forced by means ofa pump 4 and a line 6 through a' high pressure heat exchanger 8 in whichthe charging stock is passed in heat exchange with a portion of theproduct produced in the cong@ version operation. The material dischargedfrom the pump' should be at a pressure of from 550 toi800 pounds persquare inch. The preheated charging stock isy conducted from-the heatexchanger at a temperature of labout 400 F'.y and passed by means ofl aline I0 through a second l"heat exchanger I2vin Whichfthe charging stockis heated to a higher temperature by heat exchange with high temperaturevapors in the conversion process. lThe preheated voil leaves the g@ heatexchanger I2 at a temperature of labout 550 F. and is conducted througha line I 13 into and throughy a pipe coil heater mounted in a pipe stillfurnace I6. In passing throughthe pipe still furnace the naturalgasoline charging stock is g5 raised to a temperature of from 750"to 850F., and maintained at this temperatureflna portion of the coil' for asubstantial period ,of time and then discharged through a transfer lineI8'. At the temperatures and pressures given above the period of timereferred'to is preferably from 8 to 14 yminutes. l

The pipe still heaterII may be of conventionally known Aconstruction inwhich tubes of Athree or four inch internal diameter are employed, and 5in which the pressure drop" may be from 200 to 300 pounds per squareinch, lso that the pressure in the transfer line I8 will be from 250 to600 lbs. per square inch.'

The highly heated products discharged through 50. the transfer line I 8areconducted into an ejector mixing nozzle 20 mounted at the bottom ofan enlarged reaction chamber22. The products are then conducted fromtheejector 2|] through a line 24 and discharged tangentially into theup- 55 per part of the reaction chamber 22 through one or morevertically spaced lines 26.

The catalytic agent employed in the conversion operation which may, forexample be anhydrous iron phosphate or anhydrous aluminum phosphate, isintroduced into a catalyst mixing chamber 28 through a valved feet chute30, and therein intimately mixed with natural gasoline introducedthrough a valved line 32. The mixture of oil and catalytic material inthe chamber 28 may be made up continuously or in batch for use in theconversion operation,fand itmay be introduced into the conversionprocess by taking a part of the charging stock discharged from. the heatexchanger I2 through the line I 4 and passing it through a valved line34 into an ejector'nozzle 36 at the bottom of the mixing chamber 28.'I'he oil is passed at a high velocity from the line 34 and picks up thecatalytic mixture in nozzle 36.`

The oil mixture may be introduced directly into the line 24 through avalved line 38 or passed through a valved line 40 to the inlet of thepipe still heater I6 with the preheating charging stock in line I4. Inaccomplishing the latter operation the ow of oil through the lines 34,38 and 40 (including the bypass) may be controlled bythe valves in lines34 and I4, or a pump 42 mounted in line 40 may be used to force theoil-catalyst mixture from the mixing nozzle 36 into the line I4,regardless of a lower pressure in line 38.I

In carrying out the process, it is not necessary to continuouslyintroduce the catalyticmaterial into the reaction chamber 22 or into thepipe still heater, but a continuous operation may be effected by mixinga relatively small proportion of catalyst with the oil in the line I4passing to the heater I6. The prpportion of catalyst may be adjusted bycontrolling the valve in line 34.

'I'he mixture of high temperaturel products and catalyst dischargedthrough the line 26 into the upper part of the reaction chamber 22 tendto spiral'around the inside of this chamber sothat the catalyst togetherwith any small amount of liquid which may be present flows down thewalls of the chamber and collects in the conicalbottom from which thecatalyst and anyv liquid passes immediately into the nozzle 2li.A Thehigh velocity in the nozzle 20 remixes the catalytic material withtheproducts discharged from the transfer line and they are again passedinto thev upper part of the reaction chamber.

At the temperatures employed, that is preferably 800" to 850 F.maintained in the reactiony chamber22, there will be substantially noyliquid .in this chamber so that the lcatalyst will fall to the bottomof the chamber or be suspended inthe vapors in the chamber. The vaporproducts are discharged from the reaction chamber 22 through a vaportransfer line 44`andintroduced tangentially into the Aupperpart of acyclone type separator 46 in which the spent or partially spentcatalytic material is separated from the converted hydrocarbon vapormixture. The catalytic material is collected in the conical base of thisseparator anddischarged through a valved line 48, while the separatedvapors pass downwardly through the separator 46 and out through acentral enlarged conduit 50. These vapors are conducted on through aline 52y into the heat exchanger- I2 where they are substantiallyreduced in temperature to about 575 F., and then conducted through aline 54 into the base of a fractionating tower 56. i

In the tower 56 the vapors are rectified under a substantially highpressure to separate a light and gas separator 64. The separator 84 ismain-r tained under a relatively high pressure so that substantiallyonly the xed gases such as hydrogen, methane, ethane and ethylene aredischarged through a valved gas line 68. The

y condensed product passes from the receiver through a valved line 68and any portion of this product may be returned ,to the top of the tower'56 through a valved line 'I0 in which is mounted a pump 12 forcontrolling the cut temperature on the tower. l,The product dischargedthrough the'line 68 will be a relatively light gasoline having an endpoint of about 325 F. and this product is preferably blended withheavier stock and stabilized to remove any excessive quantities oflighter materials such as a portion of its propane and butane content.

The heavier condensate which refluxes downwardly through the tower 56andcollects in the bottom of the tower, is removed through a line `I4,passed through the high pressure heat exchanger 8 and finally dischargedin a cooled condition through a valved line 16. This product containssome constituents which are heavier than thosedesired in the usualgasolines. They may be eliminated by a suitable distillation, theoverhead products being available for blending with relatively-lightgasolines such as the gasoline removed through the line 68. -Theproducts removed through the-lines 68 and I6 however have octane ratingsof from 76 tov 85, increased lead susceptibility and oxygen bombstability, and therefore are particularly suitable for blending withlower octane numbered gasolines. The products are the result ofmolecular rearrangements and additions and not of decomposition.Therefore there is practically no tarry fraction formed.

'I'he pressures maintained in the receiver 64 and tower 56 will besubstantially equalto that maintained in the reaction chamber 22 exceptfor the usual pressure drop through the various intervening elements ofthe apparatus. vIt will also be apparent that the temperature andpressure in the separator 46will not be substantially different fromthat in the reaction chamberl 22 and ytherefore the conversion reactionin contact with the catalytic material will still proceed intheseparator 46. 'I'he tower 56 and the separator 46 may however beoperated at lower'pressures if desired. All of the apparatus is heavilyinsulated.

yThe theory of the action of the catalytic material .on the conversionof the parailln hydrocarbons into constituents oi.' higher octane valueis not definitely understood bu.: it may beexplained by the iniluence ofthe catalytic substances on the fected including the alkylation ofstraight chainV hydrocarbons forming branched chain as well as cyclichydrocarbons.

The spent catalyst may be revivified by Wellknown methods, such as theheating of itin a stream of air or oxygen containing gas.

From the foregoing description of the process of the present invention,it will be apparent that certain modifications of the process may bemade and that it may be carried out in apparatus substantially differentfrom that described. Low boiling oleiin hydrocarbons may be converted tomotor fuel either alone or when mixed with paraflins. Such features arevcontemplated within the spirit andsscope of. the present invention.

Having thus described the invention in its preferred form, what isclaimed as new is:

1. The process of catalytically converting a paramnic hydrocarboncontaining from three to four carbon atomsrto the molecule into amixture of hydrocarbons having a substantially` higher molecular Weight,which comprises carrying out the process in the absence of addedhydrocarbons of other type and hydrogen at a superatmospheric pressureof from 400 to 600 pounds per square inch, preheating the aliphatichydrocarbon to be converted and lmixing it with a relatively smallproportion of a solid catalytic metallic salt which is adapted tocatalyze isomerization and alkylation reactions, passing the resultingmixture in a stream of restricted cross-section through a long heatingzone in the rst part of which the mixture is heated to a temperature ofat least 750 F. and in the latter part of which the temperature issubstantially maintained and raised to a point of approximately 850 F.,discharging the resulting heated mixture into an enlarged reaction zonein which intimate contact is maintained between the hydrocarbons and thecatalytic material, passing the mixtureinto a separator in which thecatalytic material is separated from the resulting convertedhydrocarbon, and recovering the condensable products resulting from theconversion reactions.

2. The process defined by claim 1 in which the preheated mixture ispassed in a stream to a heating zone and in which said stream is dividedand one portion thereof mixed with said catalytic material andagainlunited with the other portion prior to its introduction into saidheating zone.

3. The process defined by claim 1, in which catalytic material iswithdrawn from one end of said enlarged reaction chamber and mixed witha stream of oil from the heating zone and reintroduced into the oppositeend of said reaction chamber.

4. The process dened by claim 1 in which the catalyst salt is anhydrousiron phosphate.

5. In the process of catalytically converting paraflinic hydrocarbonscontaining from three to four carbon atoms to the molecule into amixture of hydrocarbons having a substantially higher molecular weight,the improvement which comprises eectingsaid conversion at a temperatureof 750 to 850 F. and at approximately a pressure of from 250 to 600 lbs.per square inch While intimately contacting the hydrocarbons to beconverted with a catalyst adapted to catalyze isomerizatlon andalkylation reactions comprising anhydrous iron phosphate, 'andseparating the desired liquid conversion products 'from the hot productsresulting from the reaction by'cooling and condensation.

WILLIAM E. FORNEY.

